The present invention relates to polymers comprising polyether chains having a hydrophobic side chain which are linked by urethane and/or amide groups and their use as xe2x80x9cAssociation Thickenersxe2x80x9d in polar media such as paints and inks, including inks for non-contact printing processes such as Drop-on-Demand inkjet printing. Many of these polymers are believed to function according to xe2x80x9cMicellar Bridgingxe2x80x9d theory.
The terms xe2x80x9cAssociation Thickenerxe2x80x9d and xe2x80x9cMicellar Bridgingxe2x80x9d theory are explained in U.S. Pat. No. 4,426,485 and refer to the manner in which the hydrophobic parts (hereinafter hydrophobe) of a water-soluble thickener are absorbed by a solute particle such as a latex particle to provide a network of low molecular weight thickener molecules giving good flow and levelling characteristics to water-borne coatings and latex systems under high shear conditions.
Association Thickeners are thickeners which function by Micellar Bridging theory and generally contain hydrophobes which are spaced either randomly or in clusters along a hydrophilic, especially water-soluble, polymer backbone. Polyester Association Thickeners have been proposed which are obtained by polymerising a polyethylene glycol chain attached to a moiety containing a hydrophobe but these can exhibit storage deficiencies when used in strongly alkaline latices and/or latices which contain primary amines. It has now been found that improved storage properties can be obtained where the repeat units are connected via urethane and/or amide groups.
According to the invention there is provided a polymer comprising the addition reaction product of a polyisocyanate having a functionality of from 2 to 10 and a succinyl polyether having a C6-30-alk(en)yl group and at least one group which is capable of reacting with the polyisocyanate.
The polyisocyanate may be aliphatic, cyclo-aliphatic or aromatic, including mixtures thereof. Examples of suitable polyisocyanates are 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 2,2,4-trimethyl-1,6-diisocyanatohexane, 1,10-decamethylenediisocyanate, 1,4-cyclohexylenediisocyanate, 4,41-methylenebis (isocyanatocyclohexane), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane, m- and p-phenylenediisocyanate, 2,6-and 2,4-tolylenediisocyanate (TDI), xylenediisocyanate, 4-chloro-1,3-phenylenediisocyanate, 4,41-biphenyleneisocyanate, 4,41-methylenediphenylisocyanate(MDI), isophorone diisocyanate, 1,5-naphthylene diisocyanate, 1,5-tetrahydronaphthylene diisocyanate; polymethylene polyphenylisocyanates sold under the brand name xe2x80x9cPAPIxe2x80x9d such as xe2x80x9cPAPI 135xe2x80x9d (equivalent weight of 133.5 and average isocyanate functionality of 2.7) and xe2x80x9cPAPI 901xe2x80x9d (equivalent weight of 133 and average isocyanate functionality of 2.3); aromatic triisocyanate adduct of trimethylolpropane and TDI sold under the trade name xe2x80x9cMondur CB-75xe2x80x9d aliphatic tri-isocyanates such as the hydrolytic trimerisation product of 1,6-hexamethylenediisocyanate sold as xe2x80x9cDesmodur Nxe2x80x9d; and C36-dimer acid diisocyanate sold as xe2x80x9cDDIxe2x80x9d as disclosed in J. Am. Oil Chem. Soc. 51,522 (1974).
Other polyfunctional polyisocyanates are those obtainable by the addition reaction of diisocyanates and polyols such as 
or those obtainable from di-isocyanates by the biuret reaction, such as
OCNxe2x80x94(CH2)6xe2x80x94Nxe2x80x94(CONH(CH2)6NCO)2
or polyisocyanates obtainable by the cyclisation of di-isocyanates such as 
Trade product: Desmodur HL (registered Trade Mark) 
Trade product: Desmodur IL (registered Trade Mark) 
Trade product: Polurene KC (registered Trade Mark) 
Trade product: Polurene HR (registered Trade Mark) 
Tolylene diisocyanate-isophorone diisocyanate-isocyanurate Company: SAPICI) 
Trimeric isophoronediisocyanate (isocyanurate-T1890 of Chemische Werke Huls)
Further examples of polyisocyanates available as commercial products include Desmodur VL (polyisocyanate based on diphenylmethane diisocyanate (MDI) from Bayer), Desmodur A 4370 (polyisocyanate based on isophorone diisocyanate (IPDI) from Bayer), Polurene KD (polyisocyanate based on toluene diisocyanate (TDI) from SAPICI), Uronal RA.50 (polyisocyanate based on TDI from Galstaff), Polurene A (polyisocyanate based on TDI-trimethylol propane (TMP) from SAPICI), Polurene MC (polyisocyanate based on TMP-IPDI from SAPICI), Polurene MD.70 (polyisocyanate based on TMP-TDI-MDI from SAPICI.
Many of the polyisocyanates are commercially available as mixtures. The term xe2x80x9caverage functionalityxe2x80x9d means the statistical average number of free isocyanate groups in the polyisocyanate and is the ratio of average molecular weight of the polyisocyanate and the isocyanate equivalent weight taking into account the number of isocyanate groups.
Preferably, the polyisocyanate has a functionality of from 2 to 6.
The succinyl polyether is obtainable by reacting a polyether having at least one amino or hydroxy group with a C6-30-alk(en)ylsuccinic anhydride.
The polyether is preferably derivable from ethylene oxide, propylene oxide or butylene oxide or it may be derivable from polymerised tetrahydrofuran, including mixtures thereof. It is, however, preferred that the polyether is derivable from ethylene oxide and/or propyleneoxide. Polyethers derivable from ethylene oxide are much preferred. The number of recurring alkyleneoxy groups in the succinyl polyether is preferably from 4 to 800, more preferably from 4 to 500 and especially from 4 to 300.
The polyether may be a polyalkyleneglycol, a polyalkyleneglycol mono alkyl ether, a polyalkyleneglycol mono amine, a polyalkyleneglycol mono alkyl ether mono amine or a polyalkyleneglycol diamine.
When the polyether is a mono alkyl ether, the alkyl group preferably contains not greater than 30 carbon atoms, more preferably not greater than 20 carbon atoms, even more preferably not greater than 10 carbon atoms and especially not greater than 6 carbon atoms. The alkyl group may be linear or branched. Useful thickeners have been obtained when the polyether is a mono methyl ether.
It is much preferred that the polyether is difunctional. Examples of difunctional polyethers are polyalkyleneglycols, more preferably polyalkyleneglycol mono amines and especially polyalkyleneglycol diamines.
Examples of polyalkyleneglycols are polyethyleneglycols such as PEG 200, PEG 1500, PEG 2000, PEG 3000, PEG 4000, PEG 6000, PEG 8000, PEG 10000, PEG 12000 and PEG 35000, wherein the numbers indicate the approximate number average molecular weight.
Examples of mixed chain polyalkyleneglycols are the EO/PO/EO block copolymers such as those which are commercially available as Synperonic polymers from Uniqema and the PO/EO/PO block co polymers which are available as Pluronic polymers from BASF.
Examples of polyalkylene glycol mono alkyl ethers are MeO PEG 350, 550, 750, 2000 and 5000 (ex Aldrich) and nBuO PPG 340, 1000, 1200, 2500, and 4000 (ex Aldrich).
Other examples of polyalkyleneglycol mono alkyl ethers are Brij 35 (EO (23) end-capped by dodecanol), Brij 97 (EO(10) end-capped by oleyl alcohol), Brij 78 (EO(20) end-capped by stearyl alcohol) and Brij 700 (EO(100) end-capped by stearyl alcohol). The Brij surfactants are available from ICI Inc.
Examples of polyalkyleneglycol mono alkyl mono amines are the so called Jeffamine M series of polyethers available from Huntsman Corporation. Specific examples are Jeffamine M-1000 (MeO EO (19) PO (3) amine), M-600 (MeO EO (1) PO (9) amine), M-2070 (MeO EO (32) PO (10)amine), M-2005 (MeO EO (6) PO(39) and M-3003 (MeO EO (49) PO (8) amine). MeO represents a methoxy terminated polyether, EO represents repeat ethylene oxide units and PO represents repeat propyleneoxide units and the numbers in parentheses represent the approximate number of repeat units.
Examples of polyalkyleneglycol diamines are the so-called Jeffamine D-series of polyether diamines which are amine terminated polypropyleneglycols of formula 
Specified examples are Jeffamine D-230 (x=2-3), D-400(x=5-6), D-2000 (x=33 average) and D-4000 (x=68 average).
Other examples of polyalkyleneglycol diamines are the Jeffamine ED-series of polyether diamines which are based predominantly on a polyethyleneoxide backbone and of formula 
Specific examples are Jeffamine ED 600 (b=8.5, a+c=2.5), ED-900 (b=15.5, a+c=2.5), ED 2001 (b=40.5, a+c=2.5) ED-400 (b=86, a+c=2.5).
The succinyl polyether having a C6-30-alk(en)yl group is obtainable by reacting an alk(en)yl succinic anhydride (hereinafter ASA) with a polyether having at least one hydroxy or amino group. Examples of suitable succinic anhydrides are 2-octenyl, n-octadecenyl, n-decyl, n-decenyl, n-tetradecyl, n-hexadecyl, n-octadecyl, dodecenyl and polyisobutylene succinic anhydrides.
It is preferred that the alk(en)yl group contains not less than 8 and especially not less than 12 carbon atoms and preferably not greater than 24 and especially not greater than 20 carbon atoms.
Preferably the succinyl polyester contains a C6-30-alkyl group.
When the succinyl derivative is reacted with a polyether containing one or more hydroxy functional groups, the succinyl moiety is attached to the polyether via an ester group(s). When the succinyl derivative is attached to the polyether having one or more amino functional groups, the succinyl moiety is attached to the polyester via an amide or cyclic amide group(s) depending on the reaction conditions.
When the succinyl polyether is derived from a difunctional polyether such as a polyalkyleneglycol, a polyalkyleneglycol mono amine or a polyalkyeneglycol diamine the terminal carboxylic acid group of the succinyl polyether may be further reacted with an aliphatic alcohol or aliphatic amine. Preferably the aliphatic amine or alcohol contains a C6-30-alkyl group, more preferably a C8-24-alkyl group and especially a C8-20-alkyl group. The alkyl group may be linear or branched.
Examples of suitable aliphatic amines and alcohols are propylamine, n-butylamine, tert-butylamine, n-octylamine, tert-octylamine, n-decylamine, n-dodecylamine, n-octadecylaine and the polyalkylene glycol monoalkyl monoamines disclosed hereinbefore; n-propanol, tert-butanol, n-octanol, n-decanol, n-dodecanol, stearyl alcohol, the so-called Guerbet alcohols such as Isofol 12, 14T, 16, 18T, 18E, 20, 24, 28, 32, 32T and 36 (ex Condea GmbH); and polyalkyleneglycol mono alkyl monoamines and polyalkylene glycol diamines as disclosed hereinbefore.
The succinyl polyether having a terminal carboxy or isocyanate group may also be reacted with diols, diamines and/or hydroxy amines. The diol, diamine or hydroxyamine may react with the succinyl polyether to provide an Association Thickener having a free amine or hydroxy group or it may react with the two different succinyl polyether chains as a cross-linking agent. Examples of suitable diols, diamines and hydroxyamines are ethyleneglycol, polyalkylene glycols and polyalkylene glycol diamines as disclosed hereinbefore.
When the polyether is monofunctional, the ASA and polyether are preferably reacted together in stoichiometrical amounts. However, when the polyether is difunctional the ASA and polyether may be reacted together in a ratio of from 2:1 to 1:2 depending whether a succinyl polyether is required having two carboxylic acid functional groups or whether a succinyl polyether is required having two amino or two hydroxy groups. It is, however, preferred to react the ASA and difunctional polyether together in a stoichiometric ratio so that the resultant succinyl polyether contains both a carboxylic acid group and an amino or hydroxy group.
The reaction between the ASA and polyether is generally carried out in an inert atmosphere and at a temperature of from 100 to 250xc2x0 C. and preferably in the presence of a catalyst such as 4-N,N-dimethylamino pyridine. The inert atmosphere may be provided by any of the inert gases of Group VIII of the Periodic Table but is preferably nitrogen.
When it is desirable to esterify or amidate a carboxy functional group of a succinyl polyether the reaction involving an aliphatic amine or aliphatic alcohol may be carried out under similar conditions to those employed when reacting the ASA with the polyether. The esterification of a carboxy functional group of a succinyl polyether is preferably carried out in the presence of an esterification catalyst such as zirconium n-butylate.
The polymers according to the invention are obtainable by reacting one or more polyisocyanates having a functionality of from 2 to 10 with one or more succinyl polyethers which may be the same or different.
When the succinyl polyether is monofunctional it is preferred that the polyisocyanate has a functionality of not less than 3 and especially not less than 4.
However, as noted hereinbefore it is preferred that the succinyl polyether is difunctional so that the resultant polymer contains repeat segments of a succinyl polyether carrying an alk(en)yl hydrophobe connected together by polyisocyanate groups.
In one preferred aspect of the invention, the difunctional succinyl polyether is reacted in stoichiometric equivalent amounts based on the number of isocyanate groups in the polyisocyanate.
However, it will be readily appreciated that a less than equivalent amount of succinyl polyethers may be employed and residual isocyanate groups may be reacted with bifunctional cross-linking agents such as diols, diamines and hydroxyamines to give a polymer containing xe2x80x9cclusteredxe2x80x9d segments of succinyl polyether groups carrying the hydrophobe. The diols, diamines and hydroxy amines are preferably polyethers as defined hereinbefore.
Polymers containing xe2x80x9cclusteredxe2x80x9d segments of succinyl polyether groups carrying the hydrophobe are also obtainable where the polymer formed by the addition reaction of the succinyl polyether and polyisocyanate contains unreacted hydroxy and/or amino groups since these may also be reacted with additional diols, diamines and hydroxy amines in the presence of polyisocyanate.
Polymers containing xe2x80x9cclusteredxe2x80x9d segments of succinyl polyether groups carrying the hydrophobe are also obtainable where the polymer formed by the addition reaction of the succinyl polyether and polyisocyanate contains unreacted carboxylic acid groups since these may be reacted with additional diols and diamines optionally in the presence of polyisocyanate. Preferred diols and diamines are C2-10-alkylene diols and diamines and polyalkylene glycols and polyalkylene glycol diamines.
The reaction between the succinylpolyether and the polyisocyanate may be affected by any means known to the art such as heating the reactants together at a temperature from 40xc2x0 C. to 100xc2x0 C. in an inert atmosphere optionally in the presence of an organic liquid and preferably in the presence of a catalyst. Preferred catalysts are organo-tin complexes such as dibutyltindilaurate. Preferably the inert atmosphere is provided by the inert gases of the Periodic Table or preferably by nitrogen.
The organic liquid may be polar or non-polar, including mixtures thereof. Preferred non-polar organic liquids are aromatic hydrocarbons such as toluene and xylene and esters such as ethylacetate.
For maximum Association Thickening effect in aqueous latices it is preferred that the number average molecular weight of the polymer is from 10,000 to 100,000. Preferably the molecular weight is not less than 20,000 and especially not less than 30,000. It is also preferred that the molecular weight is not greater than 60,000 and especially not greater than 50,000.
Any unreacted isocyanate groups which remain in the final polymer are removed by reaction with a lower aliphatic alcohol such as propan-2-ol or n-butanol.
As disclosed hereinbefore, the polymers according to the invention have utility as Association Thickeners in polar media, and especially in aqueous systems. They may be used to thicken aqueous dispersions or emulsions of latices, especially acrylic latices. They may also be used to thicken aqueous dispersions of particulate solids, millbases, paints and inks, including inks for non-contact printing such as ink jet printing. The amount of thickener in the dispersion, emulsion, paint or ink is generally less that 5%, preferably less than 3% and especially less than 1% based on the total amount of the formulation.
The invention is further illustrated by the following non-limiting examples wherein all references are to parts by weight unless expressed to the contrary.